Consolidated Statement Of Shareholders' Equity - 9 months ended Sep. 30, 2018 - USD ($) $ in Thousands	Total	Preferred Shares	Common Shares	Additional Paid-in Capital	Accumulated Dividends in Excess of Net Income	Accumulated Other Comprehensive Income	Noncontrolling Interests	Common Shares Additional Paid-in Capital
Beginning balance (in shares) at Dec. 31, 2017		405,896	73,090,877
Beginning balance at Dec. 31, 2017	$ 2,391,514	$ 159,997	$ 733	$ 2,855,321	$ (749,367)	$ 22	$ 124,808
Increase (Decrease) in Stockholders' Equity [Roll Forward]
January 1, 2018 adoption of new accounting standard - See Note 2	(6,028)				(6,028)
Net income, excluding $2,920 attributable to redeemable noncontrolling interests	189,724				187,400		2,324
Other comprehensive income - change in fair value of interest rate swaps	105					105
Dividends declared to common shareholders	(221,623)				(221,623)
Dividends declared to preferred shareholders	(6,031)				(6,031)
Distributions declared to noncontrolling interests	(4,010)						(4,010)
Shares issued (in shares)			612,727
Shares issued	77,371		$ 6					$ 77,365
Exercise of stock options (in shares)			93,593
Exercise of stock options	4,041		$ 1	4,040
Shares issued under dividend reinvestment plan (in shares)			13,750
Shares issued under dividend reinvestment plan	1,647			1,647
Share-based compensation expense, net of forfeitures (in shares)			55,773
Share-based compensation expense, net of forfeitures	9,638		$ 1	9,637
Shares withheld for employee taxes (in shares)			(8,189)
Shares withheld for employee taxes	(927)			(927)
Conversion and redemption of OP units (in Shares)			749
Conversion and redemption of OP units	(5,906)			(528)			(5,378)
Contributions from noncontrolling interests	3,924						3,924
Ending balance (in shares) at Sep. 30, 2018		405,896	73,859,280
Ending balance at Sep. 30, 2018	$ 2,433,439	$ 159,997	$ 741	$ 2,946,555	$ (795,649)	$ 127	$ 121,668